In manufacturing processes of a semiconductor device, there is a process of forming a silicon nitride film (hereinafter, often abbreviated as a “SiN film”) on a surface of a substrate such as a semiconductor wafer (hereinafter, referred to as a “wafer”) on which an uneven (or concave and convex) pattern is formed.
The SiN film is used as, for example, a hard mask for an etching process, a spacer insulating film, a sealing film, or the like (collectively, referred to as a “protective film”). The SiN film for such uses needs to have good step coverage (SC) and small wet etching rate (WER) with respect to an uneven pattern.
In order to obtain a SiN film having good SC and small WER, it is desirable to perform a film forming process at a higher temperature to form a dense SiN film.
Moreover, when the film forming process is performed at a high temperature, a problem may occur in a raw material of the SiN film due to interaction with a substance in a base of the SiN film. As mentioned above, there may be a trade-off relationship between the film forming process at a high temperature to obtain good film quality and suppression of interaction with the substances in the base of the SiN film.
For example, in a related art, there is a method in which a silicon nitride film (SiN film) is formed on a semiconductor wafer by reaction of dichlorosilane and ammonia radical in a reaction chamber set at a temperature within a range of 200 to 410 degrees C., for example, at 400 degrees C. However, the aforementioned method does not include a technique of forming an SiN film having good film quality while taking into consideration interaction with a base of the SiN film.